Sighting apparatus.



OR 1.211.3Q9 5R W. A. BURNS.

SIGHTING APPARATUS.

APPLICATXON FILED ocT. 30. 1915.

Patented Jan. 9, 1917.

UNITED STATES PA ENT OFFICE.

WILLIAM ALBERT BURNS, OF DRUMMONDHILL, SCOTLAND.

SIGHTING APPARATUS.

Application filed. October 30, 1915.

To all whom it may concern:

Be it known that I, WILLIAM ALBERT BURNS, a subject of the King of GreatBritain, residing at Drummondhill, in the county of Inverness, Scotland,have invented certain new and useful Improvements in Sighting Apparatus,of which the following is a specification.

This invention relates to sights embodying devices to enable the line ofsight to be corrected to compensate for deviation of the projectile dueto movement of the gun platform at the moment of firing. This deviationis often known as the speed error and requires speed allowance or speedcorrection to compensate for it.

According to the first portion of the present invention, the raising orlowering of one of the sights to correct for gun platform speed iseffected automatically, as the gun is laid by mechanism of such acharacter that the ratio between the respective distances (measuredhorizontally from the two sights to a vertical plane perpendicular tothe line between them, is equal to the ratio of muzzle velocity of theprojectile to the gun-platform speed, this vertical plane passingthrough the pivot of the foresight.

In the accompanying drawings, Figure 1 is an end elevation, and Fig. 2is a side elevation of a Maxim machine gun provided with oneconstructional form of device according to the first portion of theinvention for mechanically compensating for speed error in the verticalplane only. Fig. 3 is a similar side elevation showing the position ofthe movable parts of the device when the gun muzzle is depressed 30.Fig. 4 is a side elevation of the muzzle end of a rifle fitted with amodified form of the device.

Figs. 1 and 2 show .a simple link motion by which the foresight of aMaxim gun may be raised or lowered. J represents the back sight of thegun and F the foresight. The foresight F is carried by two short links(or parallel motion arms) L L the lower arm L being actuated by an armD. This arm D is so connected by a rod R to a point on an extension Cformed on the cross-head C of the pivoting rod H, that it is alwaysparallel or at a given small inclination, as shown in Fig. 2, to thevertical axis of the pivot H. Consequently the arms L L are kepthorizontal at all inclinations of the gun assuming the gun platformitself to be horizontal. For example, as shown in Fig.

Specification of Letters Patent.

Patented Jan. 9, 1917.

Serial No. 58,911.

3, the line of sight, which was originally the line nn, is raised to theline ee. Now if the distance SP (Fig. 2) is to the forward speed of thegun platform as the distance V E L is to the muzzle velocity of the gun,this arrangement will correctly lower or raise the sight at allinclinations of the gun, to put on the required vertical speedcorrection. The distance SP may be made variable to enable the same gunto be.

used on platforms of different speeds or at different speeds of oneplatform. For this purpose the arms L L are formed with a series ofholes for the reception of pins carried by the foresight.

While this link motion system provides a relatively simple method ofeffecting the necessary vertical movement of one of the sights or oneend of a sight bar, it is to be understood that the invention is notconfined to it. For, assuming conditions to be for the moment reversedand the gun held stationary while the pivot H is swung forward andbackward around the trunnion axis, what .actually occurs is that thepartially rotary movement of the point of attachment of R and C istranslated into vertical movement of the foresight. Obviously any knownmeans by which rotary or partially rotary movement is converted intoreciprocating motion may be employed to raise or lower the sight in theaforesaid manner instead of the construction illustrated in the figures,and any such known means for this purpose may be employed.

In the case of rifles, or other small arms or machine guns, unprovidedwith a regular pivotal mounting, the connecting rod may as shown in Fig.4) be replaced by a vertical pendulum PL W for the purpose of effectingthe necessary raising or lowering of the sight. The pendulum may beinclosed in a suitable casing CS to prevent wind blowing it about, andthe casing may be partially filled with viscous liquid or other meansmay be provided to prevent minor vibrations or movement affecting thehang of the pendulum.

What I claim and desire to secure by Letters Patent of the United Statesis 1. Sighting apparatus having a foresight and a rear sight, incombination with means for automatically varying the position of one ofthe sights as the gun is being laid, said means being of suchconstruction that the ratio between the respective distances,

measured horizontally, from the two sights to a vertical planeperpendicular to the line between them is equal to the ratio of muzzle"velooity of the prgjectilemto ithe, gun-platform speed.

Q'J Sighting apparatus having a foresight and a rear sight, the formerbeing pivotally connected to a part moving in elevation with the gun, incombination with means for automatically moving the foresight as the gunis being laid, said means being of such construction that the ratiobetween the respective distances, measured horizontally from the twosights to a vertical plane perpendicular to the line between them andpassing through the point of connection between the foresight and thepart moving with the gun, is equal to the ratio of muzzle velocity ofthe projectile to the gun-platform speed.

3. Sighting apparatus having a foresight in combination with parallellink mechanism carrying the foresight from a part moving with the gun inelevation, and means for automatically actuating said link mechanism tovary the distance of the fore-sight from the gun am's to compensate forthe gun-platform speed.

4:. Sighting apparatus having a fore-sight in combination with parallellink mechanism carrying the fore-sight from a part moving with the gunin elevation and mechanism interposed between the gun and its mountingfor automatically raising and lowering the fore-sight as the gun isdepressed and elevated.

5. Sighting apparatus having a fore-sight in combination with parallellink mechanism carrying the fore-sight from a part moving with the gunin elevation, and means for automatically actuating said link mechanismto vary the distance of the fore-sight from the gun axis to compensatefor the gun-platform speed, said fore-sight being adjustable relativelyto the pivots of the link mechanism to set the apparatus to agree withdifferent gun-platform speeds.

In witness whereof, I herewith afiix my signature at New London, Conn,this 4th day of November, 1915.

WILLIAM ALBERT BURNS.

Copies of this patent may be obtained for five cents each, by addressingthe Commissioner of Patents,

Washington, D. 0.

